1. Field of Invention
The processes and apparatus of the present invention are related to (a) air conditioning with heat upgrading by an absorption operation and (b) cool thermal storage that can be charged during off peak hours of power consumption and be discharged to provide air conditioning during peak hours of power consumption.
2. Brief Description of the Prior Art
Since Immediate Heat Upgrading Absorption Air Conditioning Systems [IHUA Systems] of the present invention can provide air conditioning by absorption for big areas and small areas and can also provide cool thermal storages by storing water and concentrated absorbing solutions, prior art on (a) absorption air conditioning, and (b) cool thermal storage are reviewed in the following:
2A. Absorption Air Conditioning
A large scale absorption air conditioning process comprises (a) a step of producing a stream of chilled liquid such as water or an aqueous solution of ethylene glycol at around 7.2.degree. C. (45.degree. F.), in an absorption liquid chiller and (b) a step of circulating a stream of the chilled liquid through air handlers to remove heat from indoor air and thereby return the liquid at around 15.5.degree. C. (60.degree. F.). Manufacturers of absorption chillers are Trane Corp. in Wisconsin and Carrier Corp. in New York State. There are several manufacturers in Japan including Mitsubishi and Yasaki. A commercial absorption liquid chiller has a large vacuum enclosure enclosing (a) an evaporation zone, (b) an absorption zone, (c) a regeneration zone and (d) a condensation zone. The processing steps are as follows:
(a) As water enters the evaporation zone, flash vaporization causes formation of a first vapor and a mass of internal chilled water at around 4.4.degree. C. (40.degree. F.). An external chill water at a first temperature around 15.5.degree. C. (60.degree. F.) then exchanges heat with the internal chill water thereby cooled to a second temperature at around 7.2.degree. C. (45.degree. F.). The chilled external chill water is then circulated to air handlers and heated to the first temperature and returned to the liquid chiller;
(b) The water vapor is drawn to the absorption zone and is absorbed in a strong absorbing solution such as 65% aqueous lithium bromide solution. The absorbing solution is thereby diluted and becomes a weak absorbing solution, say 60% lithium bromide. The heat of absorption is released to a cooling water stream;
(c) The weak absorbing solution then enters the regeneration zone, wherein it is heated and vaporized to generate a second water vapor and becomes a strong absorbing solution that is heat exchanged and returned to the absorbing zone;
(d) The second water vapor is condensed by rejecting heat to a cooling water stream and the condensate formed is heat exchanged and returned to the evaporation zone.
The operations in a small conventional absorption air conditioner are similar to those of a larger unit described, except that the internal chilled water produced in the evaporation zone is circulated directly to an air handler.
In contrast, a system of the present invention uses one or more Immediate Heat Upgrading Air Handlers, in which latent heat of vaporization is taken directly from indoor air or outdoor air without forming an intermediate chill water streams.
2B. Cool Thermal Storage
Chilled water, ice or a phase change material can be used as a cool storage medium. During a charging period, a cool storage medium is cooled and taken to a low enthalpy state, such as chilled water, ice, hydrate crystals; during a discharging period, the medium is heated and taken to a high enthalpy state. In contrast, during a charging period, the cool storing medium of a system of the present invention is taken to a high free energy state, i.e. strong absorbing solution and water, and during a discharging period, the medium is taken to a low free energy state, i.e. a weak absorbing solution. The conventional systems are described as follows;
(a) Chilled Water Storage Systems
Conceptually, chilled water storage appears to be simple. The major drawback is that the mass of water needed to provide a given cool storage capacity is large. Water stores cooling capacity by a decrease in its temperature. Chilled water storage is traditionally designed on a 11.1.degree. C. (20.degree. F.) temperature rise. Therefore, it takes almost 283 liters (10 ft.sup.3) of water to provide one ton-hour of cool storage capacity.
(b) Static Ice Storage Systems
In a static ice storage system, ice is made on tubes by an indirect freezing operation and is melted in place by circulating water to thereby produce chilled water for air conditioning. The volume of ice must be permeated with channels of fluid to transport heat into and out of the body of ice. A major manufacturer of static ice storage systems is CALMAC Manufacturing Corporation of Englewood, N.J.. CALMAC Corporation uses water chiller manufactured by Trane Company in its ice storage systems.
(c) Dynamic Ice Storage Systems
In a dynamic ice storage system, ice is produced by a flake ice machine and flake ice is stored in a vessel. A stream of circulating water is brought in contact with flake ice to be chilled and returned for cooling process equipment or a building. Major manufacturers of dynamic ice storage systems are Turbo Company in Denton, Tex. and Mueller Company in Springfield, Mo.
(d) Slushy Ice Storage Systems
In a slushy ice storage system, a slushy ice mixture is formed by an indirect freezing operation. A mass of slushy ice may be directly circulated for air conditioning or a water stream may be chilled by the slushy ice and used for air conditioning. Developers of slushy ice systems are Chicago Bridge and Iron Company in Chicago, IL. and Sunwell Engineering Company in Canada.
(e) Eutectic Salt Storage Systems
Eutectic describes a mixture of compound easily fused or fusing at the lowest possible temperature. The eutectic salt used in thermal storage application is a salt hydrate that fuses at 47.degree. F. In a crystalline form the salt fuses with several water molecules. In the amorphous form the salt dissociates from the water molecules, or "melts". Energy in the form of heat must be added to the hydrate to cause the dissociation. Transphase Systems, Incorporated in Huntington Beach, CA is a major supplier of eutectic cool storage systems.
(f) Vacuum Ice Storage
A vacuum ice storage system has been invented by Chen-Yen Cheng and is described in U.S. Pat. No. 5,059,228 issued on Oct. 22, 1991. The system comprises a vacuum vessel, a multitude of adiabatic ice making trays, a set of condenser tubes or plates and a set of vapor generating surfaces. During a charging period, refrigerant liquid is vaporized inside of the condenser tubes or plates. A part of the water in the adiabatic trays vaporizes to cause remaining water to freeze on the trays and the vapor is desublimed on the condenser surfaces. During a discharging period, a mass of external water is heat exchanged with a mass of internal water to cause vaporization of the internal water and thereby form a vapor which pressure is somewhat higher than the triple point pressure of water. The vapor so formed enters the adiabatic trays to melt the ice on the trays.